1. Field of the Invention
This invention relates to a composite wire for stainless steel welding, and more particularly to a wire for use in gas-shielded arc welding which provides a high degree of separability of slag from the surface of beads.
2. Description of the Prior Art
Inert gases, for example, Ar, He and CO.sub.2 (partially mixed with O.sub.2) are widely used alone or in combination as a shield gas in the art of gas-shield arc welding. For example, MIG welding in an inert gas atmosphere requires the use of a slight amount of CO.sub.2 gas or O.sub.2 gas due to the fact that the arc is less stable though the appearance of beads is satisfactory without formation of any slag. This leads to increased workability but results in the disadvantage that alloy ingredients tend to be oxidized and become exhausted readily in moving in the form of droplets and finally attach in part to the surface of the beads in the form of a slag. With a Cr containing alloy as used in welding stainless steels, a high melting point slag containing chromium oxide is developed and attached tightly to the surface of the beads. Failure to remove the slag prior to the welding of a next succeeding layer results in blow-holes, inferior fusion, etc. and the procedure of slag removal is therefore mandatory. An obstinate slag could only be removed by grinding or other hard work. We proposed, in Japanese laid-open Patent Application 129188/1978 for instance, a wire providing for easy slag separation, and has made further studies.